Traditional telephony services provided by digital switches, such as digital multiplexing switches, have reached their functional limits with existing user interfaces, which essentially are telephone sets having limited displays and simple keypads. Further, the telephone sets have limited bandwidth. Over newer packet networks, multimedia services are flourishing and are capable of exploiting the capabilities of advanced user terminals, desktop computers, and network appliances.
Currently, the vast majority of voice telephony is provided, at least in part, by traditional circuit-switched networks. Given the extensive infrastructure, reliability, and quality of service, these traditional telephony systems are likely to remain a significant part of voice communications for the foreseeable future. Unfortunately, there has been difficulty integrating voice sessions over the traditional telephony network with multimedia sessions over packet networks. In particular, there is a desire to associate multimedia devices with telephony devices, such as telephone terminals, and create multimedia sessions related to a voice connection. Users prefer the traditional telephony network for voice, yet the voice network is unacceptable for facilitating advanced multimedia services, such as screen sharing, video conferencing, and the like. Given the unique strengths of the respective communication systems, there is a need for an efficient and economical way to facilitate interworking between the networks. There is a further need to facilitate such interworking without requiring significant changes to the traditional telephony or packet-switched infrastructures and communication protocols.
Further, a large number of enterprises use public branch exchanges (PBXs) to provide most of the telephony services to the employees of that enterprise as opposed to relying on the public network telephony switch. In a typical situation, the PBX is involved in all calls within the enterprise while the public network telephony switch is used only for calls in and out of the enterprise. These enterprise users are also typically those most likely to want to combine traditional telephony services with multimedia services to improve employee productivity. Many functions or features provided by a traditional switch may be unavailable to enterprise users serviced by a PBX. Accordingly, those users most likely to need to combine multimedia and traditional telephony services are even further removed from such capability. Thus, there is also a need to facilitate interworking between public and enterprise systems.